Rectifier anode



2 Sheets-Sheet l REGTIFIER ANoD'E March l0, 1942. l.. A. KILGORE ETAL Filed March 16, '1940 INVENTORS Lee fl. /zqore and Hefg/Yy /Wyers.

^ AJM/5% ATTORNEY WITNESSES:

2 Sheets-Sheet 2 Marlhlo 1942- L. A. KILGORE ErAL RECHNER ANoDE Filed March '16, 1940 WITNESSES: /UW- Patented Mar. 10, 1942 UNITED STATES PATENT OFFICE RECTIFIER ANODE Application March 16, 1940, Serial No. 324,386

51Claims.

Our invention relates to a. highcurrent anode connection and, particularly, to the lead-in connection for the anode of a lmercury-vapor rectier.

In the operation of mercury-vapor rectiers, the current limitations are determined by the stresses in the insulating bushings separating the anode stems from themain body ofthe recter vessel. It has heretofore .been customary to construct the anodes of carbonaceous.y material, such as graphite, which can satisfactorily be operated at a temperature of approximately 900 C. In order to secure suitable electrical conductivity, it has heretofore been customary to construct the anode stem of a metal of high electrical conductivity such as a copper bar of a diameter of approximately 11/2 inches. Since copper isa relatively good conductor of heat, it follows that this copper lead-in is at a temperature closely approximating that of the anode.

In order to prevent destruction of .theanode bushing, several means have heretofore been resorted to to cool that portion of the stem which is in contact with the bushing and in order to prevent destruction of the usual seals, these seals are artificially cooled in any suitable manner, usually by the provision of a liquid cooled -adjacent the seal. However, in these constructions, the anode stem being at a high temperature radiates heat to the innersurface of theanode bushing so that the anode bushing tends to expand. However, the outer surface of the bushing is at a much cooler state, resulting in stresses which heretofore have frequently damaged the anode bushings.

It is an objectof our invention `to provide an articulated anode stem having the necessary high electrical conductivity by providing at least a portion of the stem beyond the inner end of the anode bushing with a section having a high thermal resistivity so that that portion of the anode stem within the anode bushing is at a much lower temperature than heretofore has been the case. We have alsov found that thevthermal stress of the insulator may be reduced by. providing a suitable metal shield between the anode stem and the anode bushing. This shield is preferably made of non-magnetic iron in order to prevent a reactance effect by the shield on the stem.

Other objects and advantages of our invention will be apparent from .the following detailed description, taken in conjunction with the accompanying drawings, in which:V

Figure 1 is a sectional elevation of an ignition type rectier having an anode construction according to our invention; and

Fig. 2 is a similar View of a modified stem according to our invention.

In the illustrative embodiment of our invention according to Fig. 1, the converter comprises a suitable metallic vessel I inthe bottom of which is housed a reconstructing cathode 2 of suitable vaporizable material, such as mercury or gallium. Cooperating with the cathode 2 is a suitable exciting mechanism herein illustrated as a makealive electrode 3 in contact With the cathode 2. In opposed relation to the cathode 2 is a suitable anode herein illustrated as a graphite body 4 suspended/at the end of a suitable articulated lead-in connection or anode stem '5, the upper portion 6 of the anode stem 5 being constructed of a copper rod which is sealed in vacuum-tight relation to a ceramic or other suitable insulating bushing 'I provided between the anode stem 5 and the main body of the rectifier vessel I. The bushing I is also sealedin vacuum-tight relation to the rectifier vessel I, preferably also by means of a suitable solder seal 8.

In order to provide a section of high thermal resistivity, that end 9 of the anode stem 5 extending beyond the skirt I0 of the anode bushing 'I is constructed of a material, such as Monel metal, which has a high thermal resistivity and which isinert in the presence of heated graphite.

y In constructing the anodestem, the copper portion 6 may be bored out to provide an internal opening I`I while therMonel metal 9 is machined to` provide a tight fitting insert I2 substantially filling the opening I'I. Suitable grooves I3 may be provided and filled with suitable brazing material after which the portions may be pressed together and secured in assembled relation by heating the entire anode stem 5 in a-suitable high temperature furnace.

Inorder to further protect the bushing I from the temperature of the anode stem 5, a suitable metallic shield I5 preferably composed of nonmagnetic stainless steel, is inserted in spaced relation to both the anode stem and the skirt I!) of the bushing l.

A suitable radiator I6 is preferably applied to the cuter end of the anode stem 5, so that the cuter end of the anode stem 5 is maintained at a temperature lower than the permissible temperature of the material composing the seal 8 between the anode stem 5 and the outer end of the anode bushing 'I.

In the operation of the converter equipped with our articulated :anode stem 5, the anode head I can [be operated at a temperature of at least 960 C. while the thermal resistivity of the lower end of the anode stem 5 decreases the temperature of the copper portion of the stem 5 to approximately 250 C. The radiator I5, therefore,

" should be constructed of ample proportions to reduce the temperature of the outer end of the stem 5 to a suitable temperature. The non-magnetic shield I5 prevents direct radiation from the anode stem 5 to the bushing 1.

In the modification according to Fig. 2, the

bushing is provided with a relatively short skirt terminating adjacent the inner edge of the rectiiier vessel I and a high resistivity insert 20 is composed of a metal, such as stainless steel, which may be assembled in any suitable manner with the copper stem 6 which is preferably provided with a threaded engagement 2l and then welded to make a iir-m mechanical and electrical union between the stainless steel and copper. It has been found that when the anode stems or that portion of the stem in contact with the graphite head is constructed of iron and is heated to approximately 900 C., the iron from the stem goes into solution with the carbon of the head, producing a low melting alloy which will flow into the cathode and may eventually completely destroy the device. In order to prevent such action when the steel insert 20 is utilized, that portion 22 of the stem in actual engagement with the graphite head 4 is composed of copper in the same manner as the upper portion of the stem is constructed of copper.

While for purposes of illustration, we have shown and described specific embodiments of our invention, it will be apparent that changes and modifications can be made therein without departing from the true spirit of our invention or the scope of the appended claims.

W e claim as our invention:

l. A vapor-electric device comprising an evacuated container, a vaporizable reconstructing cathode therein, an anode therein, an anodestem, a vacuum-tight bushing of insulating material for supporting said anode-stem as it passes through the top of said container, and means for causing an arc-discharge between said anode and cathode; said anode-stem having a junctionmeans for securing it within said bushing, said bushing having a tubular skirt-portion depending from said junction-point and surrounding a portion of the anode-stem in spaced relation thereto, substantially all of said skirt-surrounded portion of the anode-stem being of a cross-section and material such as to give it a good thermal conductivity so as to minimize the temperature-differences imposed on diierent portions of the surrounding skirt-portion, and said anode-stem having a second portion between said skirt-surrounded portion and the anode arranged with such cross-section and material somewhere therein so as to have a relatively poor thermal conductivity so as to cause a relatively large temperaturedrop in said second portion.

2. A vapor-electric device comprising an evacuated metallic container, a vaporizable reconi structing cathode therein, a graphite anode spaced from said cathode, an anode-stem extending through the top of said container, a vacuum tight insulating bushing surrounding a portion of said anode-stem means for securing said anode-stem in said bushing at a point remote from the anode, a vacuum seal between said bushing and said container, a second vacuum seal between said bushing and said anode-stem, that portion of the anode-stem surrounded by the bushing being constructed substantially of copper, a second portion of said anode-stem extending from said copper portion into contact with the anode, said second portion being constructed of Monel metal.

3. A vapor-eelctric device comprising an evacuated metallic container, a vaporizable reconstructing cathode therein, a graphite anode spaced from said cathode, an anode-stem connected to said anode, there being an opening in said container, said anode stem extending through said opening, an insulating bushing surrounding said anode-s-tem and closing said opening, said bushing terminating in spaced relation to said anode, means for securing said anodestem to 'said bushing at the end of the bushing remote from the anode, said bushing being spaced from the anode-stem throughout the major portion of its length, that portion of the anodestem which is surrounded by the bushing being constructed of copper, and that portion of the stem extending between the bushing and the anode being constructed at least in part of a material having a relatively poor thermal conductivity.

4. A vapor-electric device comprising an evacuated metallic container, a vaporizable reconstructing cathode therein, a graphite anode spaced from said cathode, an anode-stern connected to saidv anode, there being an opening in said container, said anode-stem extending through said opening, an insulating bushing surrounding said anode-stem and closing said opening, said bushing terminating in spaced relation to said anode, means for securing said anodestem to said bushing at the end of the bushing remote from the anode, said bushing being spaced from the anode-stem throughout the major portion of its length, that portion of the anode-stem which is surrounded by the bushing being constructed of copper, that portion of the stem extending between the bushing and the anode being constructed at least in part of a material having a relatively poor thermal conductivity, and a shield of non-magnetic steel extending from said securing means and said anode, said shield being spaced from said anode-stem and said bushing,

5. A vapor-electric device comprising an evacuated metallic container, a mercury cathode in said container, a graphite anode cooperating with said cathode, an anode-stem connected to said anode and extending through the Wall of said container, a bushing of insulating material surrounding a portion of said anode-stem at the point where it passes through the container wall, said bushing terminating in spaced relation to said anode, means for supporting said anodestem on said bushing, a solder seal between said anode-stem and said bushing, a second solder seal between said bushing and said container, a radiator secured to said stem externally of said container, that portion of the stem surrounded by the bushing being constructed substantially of copper and having a cross Section area such as to minimize the temperature gradient along the bushing surrounded portion, that portion of the stem extending between the bushing and the anode being constructed of a material having a relatively poor thermal conductivity so as to cause a large temperature gradient in said portion extending between the bushing and the anode.

LEE A. KILGORE. HENRY C. MYERS. 

